Mohammed et al
Tropical Journal of Pharmaceutical Research August 2013; 12 (4): 617-621
ISSN: 1596-5996 (print); 1596-9827 (electronic)
© Pharmacotherapy Group, Faculty of Pharmacy, University of Benin, Benin City, 300001 Nigeria.
All rights reserved.
Available online at http://www.tjpr.org
http://dx.doi.org/10.4314/tjpr.v12i4.26
Original Research Article
Incidence and Antibiotic Susceptibility Pattern of Bacterial
Isolates from Wound Infections in a Tertiary Hospital in
Nigeria
Aisha Mohammed, Gbonjubola O Adeshina* and Yakubu K Ibrahim
Department of Pharmaceutics and Pharmaceutical Microbiology, Ahmadu Bello University, Zaria, Nigeria
*For correspondence: Email: [email protected]; Tel: +234-8037880000
Received: 18 October 2012
Revised accepted: 17 June 2013
Abstract
Purpose: To investigate the incidence of different bacteria isolates in 150 wound infections
in Aminu Kano Teaching Hospital, Kano, Nigeria and their antibacterial
susceptibility patterns.
Methods: Wound swab samples were collected from general culture bench of the Microbiology
Department, after obtaining consent from the hospital’s Medical Advisory Committee, and cultured for
bacterial isolates. The isolates were characterized and identified by standard microbiological methods.
Antibiotic susceptibility testing was carried out using Kirby-Bauer-CLSI modified Disc Agar Diffusion
technique.
Results: Out of the 150 specimens collected, 82 % were infected with bacteria made up predominantl
of Staphylococcus aureus (22 %), Pseudomonas aeruginosa (19.9 %), Citrobacter spp (15 %),
Escherichia coli (14.7 %) and Proteus mirabilis (14.5 %). In vitro antibiotic susceptibility tests showed
that Pseudomonas aeruginosa was susceptible to ceftazidime, ciprofloxacin and gentamicin while the
enteric bacteria were generally more resistant to ceftazidime, gentamicin and ciprofloxacin.
Conclusion: The findings show that there is a high rate of wound infection in Kano, Nigeria and that
antibiotic-resistant bacteria are present in the wound sites.
Keywords: Wound infection , Antibiotic, Susceptibility, Bacterial resistance
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INTRODUCTION
The introduction of antibiotics has reduced
mortality rates which were on the high side due
to life-threatening diseases, especially infections.
Enlightenment on the use and management of
antibiotics cannot be overemphasized as it will
continue to be the way out of many infections
which occur frequently in plants and animals
including humans. Increase in the misuse and
mismanagement of antibiotics which are now
leading to drug resistance is creating a lot of
concern in medical practice. The current spread
of multi-drug resistant bacterial pathogens has
added a new dimension to the problem of wound
infections [1]. This is particularly worse in
resource-poor countries where sale of antibiotics
is poorly controlled [2].
Infection of wound is the successful invasion,
proliferation by one or more species of
microorganisms anywhere within the body’s
sterile tissues, sometimes resulting in pus
formation. Development of wound infection
depends on the interplay of many factors. Wound
infections may occur following accidental trauma
and injections, but post-operative wound
infections in hospital are most common. Some
infections are endogenous in which infection
Trop J Pharm Res, August 2013;12 (4): 617
Mohammed et al
occurs by patient’s own bacterial flora such as
Staphylococcus aureus from skin and anterior
nares or coliforms.
Many infections are exogenous, with skin and
anterior nares of the nostrils being important
sources of Staphylococci. Spread of organisms
from hospital staff and visitors occur by direct
and indirect airborne routes. Certain parasite
(e.g.,
Hookworm
larvae)
and
bacteria
(Treponema pallidum) can penetrate intact skin,
but certain primary skin infections like impetigo is
caused by Streptococcus pyogenes or
Staphylococcus aureus, or both gaining access
to abrasions as minor trauma to skin is a part of
everyday life [3].
Organisms commonly found in infected wounds
include Gram positive cocci such as S. aureus,
Streptococcus spp, Gram negative bacilli mostly
Acinetobacter, Enterobacter, E. coli, Proteus spp,
Ps. aeruginosa and anaerobic bacteria such as
Propionibacterium spp. and Klebsiella spp. [4].
This study therefore aims at investigating the
incidence of wound infection in Kano, Nigeria
and the antibiotic susceptibility of the possible
bacterial isolates to commonly prescribed
antibiotics in the locality.
EXPERIMENTAL
Study area
This study was carried out at Aminu Kano
Teaching Hospital (AKTH), Kano in Northwestern
Nigeria. It is the largest tertiary health institution
in Kano State with a bed capacity of four hundred
and twenty two.
Ethical considerations
In accordance with the International Ethical
Guidelines for Biomedical Research Involving
Human Subjects [5], ethical approval for this
study
with
number
NHREC/21/08/2008a/
AKTH/EC/210 was obtained from the Medical
Advisory Committee of the Aminu Kano Teaching
Hospital, Kano, Nigeria.
Sample size
A total of 150 wound swabs submitted at the
general culture bench from in-patients in different
wards of the hospital, 76 of which were male and
74 female. Inclusion criterion was patients with
purulent wounds.
Culture of specimen
The specimens were inoculated on blood,
chocolate and MacConkey agar plates (Oxoid,
Basingstoke, U.K) . The plates were incubated
aerobically at 37 0C for 24 to 48 hours. Pure
colonies were kept in nutrient agar slants. The
nutrient agar slants were incubated at 37 oC for
18 – 24 h before storage in the refrigerator at 4
°C pending biochemical analysis.
Identification of bacterial pathogens
Pure cultures were characterized using
morphological appearances on selective and
differential media. Motility test and biochemical
tests such as catalase, coagulase, oxidase,
Voges Proskauer, hydrogen sulphide production,
urease, methyl red, indole, citrate and sugar
utilization tests were carried out according to
standard techniques [6].
Antibiotics
A total of five (5) antibiotics, which represent the
most commonly prescribed antibiotics for
treatment of wound infections in the study area,
were used in the study. Oxoid antibiotic discs
used were amoxicillin (AMX, 10 µg), ceftriaxone
(CRO, 30 µg), ceftazidime (CAZ, 30 µg),
ciprofloxacin (CIP, 10 µg) and gentamicin (CN,
30 µg).
Antibiotic susceptibility test
This was carried out using Kirby-Bauer-CLSI
modified disc agar diffusion technique (DAD) [7].
One milliliter (1.0 ml) of standardized overnight
culture of each isolate (containing 106 CFU/ml)
was used to flood the surface of Mueller Hinton
Agar (MHA) plates and the excess drained off.
The plates were left to dry. The standard
antibiotic discs were then aseptically placed at
reasonable equidistance on the inoculated MHA
plates and allowed to stand for 1 h. The plates
(prepared in duplicates for each isolate) were
then incubated at 37°C for 18 h. The diameter of
the zones of inhibition produced by each
antibiotic disc was measured and recorded after
incubation.
Determination of the multiple antibiotic
resistance index (MARI):
Multiple antibiotic resistance index (MARI) was
determined for each isolate by dividing the
number of antibiotics to which the organisms is
resistant by the total number of antibiotics tested
[8].
Trop J Pharm Res, August 2013;12 (4): 618
Mohammed et al
Statistical analysis
Data were processed with Microsoft Excel 2010.
and general descriptive analysis, and correlation
coefficient was used to analyze occurrence and
extent of factors using Microsoft Excel 2010. P <
0.05 was considered significant.
RESULTS
Relatively higher proportion of samples from
male patients yielded isolates. Ten (10) of the
positive samples yielded two isolates on
culturing. Gender distribution of patients with
wound infections from October 2010 – December
2010 showed that out of seventy-six wound
samples from male patients sixty-five (85.5 %)
yielded bacterial isolates while fifty-eight (78.4 %)
out of the seventy-four samples from the female
patients yielded bacterial isolates. The difference
was not statistically significant.
Surgical sites were the most frequently infected,
accounting for 35 % of overall infection Burns
and wound sepsis accounted for a cumulative of
about 40 %. Diabetic ulcers were the least sites
with infection (Figure 1).
aureus in diabetic ulcers. For surgical sites, there
was a predominance of Enterobacteriaceae and
Ps. aeruginosa.
High level of resistance against amoxicillin was
observed among the organisms. Resistance to
ciprofloxacin and gentamicin was observed to be the
lowest among the organisms. Ceftazidime was
observed to be the most active against Ps.
aeruginosa.
Resistance
to
gentamicin
and
ciprofloxacin was observed to be low amongst the S.
aureus isolates. However, the Enterobacteriaceae
especially E. coli isolates generally showed a high
level of resistance against the test antibiotics (Table
2).
DISCUSSION
The distribution of wound contaminants in the
prospective study which showed that S. aureus,
Ps. aeruginosa, Citrobacter spp, Pr. mirabilis and
E. coli are the predominant contaminating
organisms is in agreement with the findings of
Sani et al [10]
Figure 1: Distribution (%) of bacteria isolates from
different wound sites of patients attending Aminu Kano
Teaching Hospital from October – December 2010
Surgical wounds sites with high bacterial
contaminants constitute a serious problem in the
hospital especially in surgical practice where
clean operations can become contaminated and
subsequently infected. The degree to which
surface wounds are infected by surrounding
bacteria contaminants have become clinically
important [4]. The predominance of Gram
negative bacilli in surgical site infection (SSI) in
this study is similar to that of Mofikoya et al, [11].
In most cases of SSI, the organism is usually
patient’s endogenous flora. In abdominal
surgeries, the opening of the gastrointestinal
tract increases the likelihood of coliforms and
Gram negative bacilli as agents of wound
infection which was the finding in this study.
These groups of organisms tend to be endemic
in hospital environment by being easily
transferred from object to object and they also
tend to be resistant to common antiseptics, often
difficult to eradicate in the long term [11]. This
does not agree with the work of Jonathan et al
[12] who reported S. aureus as the predominant
isolate. Enterobacteriaceae are increasingly
playing a greater role in the many hospital
acquired infections [11].
Table 1 shows that the predominant
contaminating organisms differ, depending on
the wound type/site. The most predominant
organism in wound sepsis was S. aureus, while
in burns; the most predominant organisms were
S. aureus and Ps. aeruginosa. In non–diabetic
ulcers, the most predominant organisms were Pr.
mirabilis, E. coli, and S. aureus as against Ps.
aeruginosa, Citrobacter spp, E. coli, and S.
Staphylococcus aureus was the predominant
organism in wound sepsis. This finding is in
agreement with the works of Mashita et al [13]. In
burn wounds, both S. aureus and Ps. aeruginosa
were the most prevalent as has been reported by
others in the past [14]. The type of organisms
isolated from ulcers and diabetic ulcers such as
Ps. aeruginosa, S. aureus, Citrobacter spp and
E. coli in a prospective study is similar to findings
Trop J Pharm Res, August 2013;12 (4): 619
Mohammed et al
Table 1: Distribution (%) of organisms at different infected wound sites
Bacteria isolates
Wound
sepsis
27.8
0.0
0.0
0.0
5.3
7.1
23.8
0.0
48.4
11.1
E.coli (n = 18)
Salmonella spp (n = 1)
Providencia spp (n = 2)
Pr. vulgaris (n = 5)
Pr. mirabilis (n = 19)
Ps. aeruginosa (n = 28)
Citrobacter spp (n = 21)
Enterobacter spp (n = 7)
S. aureus (n = 31)
Klebsiella spp (n = 9)
Distribution at different wound sites
Burns
Ulcers
Diabetic
ulcers
5.6
22.2
11.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
20.0
21.0
26.3
0.0
32.1
7.1
14.3
14.3
4.8
9.5
28.6
0.0
0.0
29.0
9.6
6.5
33.4
22.2
11.1
Surgical
sites
33.3
100
100
80.0
47.4
40.0
47.6
71.4
6.5
22.2
Table 2: Resistance (%) of bacterial isolates to selected antibiotics
Bacteria isolates
Resistance to selected antibiotics (%)
Amx
Ctx
Ctz
Cip
Gen
Ps. aeruginosa (n = 28)
S. aureus (n = 31)
Klebsiella spp (n = 9)
Enterobacter spp (n = 7)
Citrobacter spp (n = 21)
E. coli (n = 18)
Pr. mirabilis (n = 19)
Pr. vulgaris (n = 5)
Salmonella spp (n = 1)
100
100
100
100
67
94
68
100
100
18
29
56
57
57
89
26
0
0
21
29
78
71
57
89
21
50
0
46
52
56
86
76
89
32
20
100
4
84
67
86
81
89
37
20
100
Key: Amx = Amoxicillin, Ctx = Ceftriaxone, Ctz = Ceftazidime, Cip = Ciprofloxacin, Gen = Gentamicin Values
presented in Table 3 shows that a high proportion of the wound bacterial isolates were multiple antibiotic resistant
(i.e., had MARI ˃ 0.2). While S. aureus, Salmonella spp, Enterobacter spp, Citrobacter spp, Klebsiella spp and E.
coli isolates were multi – antibiotic resistant isolates. Proteus spp and to a lesser extent Providencia spp were
less resistant to multiple antibiotics.
Table 3: Multiple Antibiotic Resistance Index (MARI)
of bacteria isolates from wound infections (based on
the antibiotics in Table 2 above)
Bacteria isolate
Ps. aeruginosa (n=28)
S. aureus (n=31)
Salmonella spp (n=1)
Klebsiella spp (n=9)
Providencia spp (n=2)
Enterobacter spp (n=7)
Citrobacter spp (n=21)
E. coli (n=18)
Pr. mirabilis (n=19)
Pr. vulgaris (n=5)
% with
MARI ˃ 0.2
60.7
90.3
100
77.8
50.0
100
85.7
88.9
42.1
40.0
hospitalized patients include: the prior use of
antibiotic, broad spectrum antibiotics, prolonged
hospital stay and the presence of invasive
medical devices. Other factors include the
spread
of
resistant
organisms
through
overcrowding and inadequate hospital infection
control practices [19].
of Fadeyi et al [15] and Vimalin and Growther
[16]. Pseudomonas aeruginosa and S. aureus
have been implicated in wound sepsis by a
number of researchers [17,18].
There was general resistance to amoxicillin by
the wound bacterial isolates, which might be due
to the pressure of prolonged usage and regular
abuse in our society. This is not unconnected
with the abuse of amoxicillin by the populace
since antibiotics are still sold across the counter
in some pharmaceutical and patent medicine
stores in Nigeria. The recent surge in the
widespread use of ceftriaxone, a broad spectrum
cephalosporin, in this region for empirical
treatment could explain the increase in the
resistance level observed in this study [20].
Generally, inadequate antimicrobial treatment
defined as ineffective treatment of infection is an
important factor in emergence of antibiotic
resistant bacteria. Factors that contribute to
inadequate
antimicrobial
treatment
of
The low level of resistance shown by the Ps.
aeruginosa
isolates to ceftazidime (a third
generation cephalosporin), ciprofloxacin and
gentamicin indicates that these three drugs are
still effective in this region compared to other
Trop J Pharm Res, August 2013;12 (4): 620
Mohammed et al
studies which showed, for example, that Ps.
aeruginosa is highly resistant to gentamicin [21].
A high sensitivity profile to ciprofloxacin and
gentamicin has also been reported by Taiwo et al
[4]. It is gratifying to note that S. aureus isolates,
which were the most predominant species
among the wound bacterial contaminants were
sensitive to gentamicin and ciprofloxacin. A
similar observation was reported by Taiwo et al
[4]. These antibiotics, therefore, are still relevant
in the treatment of wound infection in this study
area.
CONCLUSION
The study showed that S. aureus, Ps. aeruginosa
and enteric bacteria are the major agents found
in infected wound site in AKTH, Kano, Nigeria,
Nigeria. The bacteria isolates are generally
resistant to β-lactam antibiotics but gentamicin
and ciprofloxacin are effective against the
isolates. However, bacterial isolates which were
not readily susceptible to commonly used
antibiotics, such as amoxicillin and ceftriaxone,
were present in the study environment.
REFERENCES
1. Sule AM, Olusanya O. In-vitro antimicrobial activities of
fluoroquinolones
compared
with
common
antimicrobial agents against clinical bacterial
isolates from parts of South Western Nigeria. Nig
Quarterly J Hospital Med 2000; 10 (1): 18-21.
2. Onile BA. Rational use of antibiotic/antimicrobial agents.
Nig Med Practice 1997; 33(2): 2-4.
3. Bhatt CP, Lakhey M. The distribution of pathogens
causing wound infection and their antibiotic
susceptibility pattern. J Nepal Health Res Council
2007; 5(1): 22-26.
4. Taiwo SS, Okesina AB, Onile BA. In-vitro antimicrobial
susceptibility pattern of bacterial isolates from
wound infection in University of Ilorin Teaching
Hospital. Afr J Clin Experimental Microbiol 2002;
3(1): 6-10.
5. International Ethical Guidelines for Biomedical Research
Involving Human Subjects: Prepared by the
Council for International Organizations of Medical
Sciences (CIOMS) in collaboration with the World
Health Organization (WHO), Geneva 1993.
6. Cowan, S. T. and Steel, K. J. (1993). Cowan and Steel’s
rd
manual for identification of medical bacteria.3
edition Cambridge University Press. London. PP.
199-241.
7. Cheesbrough M. Microbiological tests. In: District
laboratory practice in tropical countries. 2nd ed.
U.K: Cambridge University Press; 2006; p 189.
8. Paul SB, Roy RL, Ghosh AC. Multiple Antibiotic
Resistance (MAR) index and its
reversion in
Pseudomonas aeruginosa.
Letters in Applied
Microbiol 1997; 24: 169-171.
9. Sani RA, Garba SA, Oyewole OA. Antibiotic resistance
profile of Gram negative bacteria isolated from
surgical wounds in Minna, Bida, Kontagora and
Suleja Areas of Niger State. Am J Med Med Sci
2012; 2(1): 20-24.
10. Qureshi AH, Rafi S, Qureshi SM, Maqsood. The current
susceptibility pattern of MRSA to conventional
antistaphylococcus antimicrobials at Rawalpindi.
Pakistan
J Med Sci 2004; 20: 361–364.
11. Mofikoya B, Neimogha M, Ogunsola F, Atoyebi O.
Bacterial agents of abdominal
surgical site
infections in Lagos Nigeria. Eur J Sci Res 2009;
38(3): 509-513.
12. Jonathan OI, Ashietu O, Adevbo E, Rachael O, Ahmadu
T. Incidence of aerobic bacteria and Candida
albicans in post-operative wound infections. Afr J
Microbiol Res 2008; 2(2): 288-291.
13.
Mashita K,
Shinagawa N,
Sato T,
Hirata K,
Katsuramaki T,
Mukaiya M,
Yura J.
Bacteria isolated from surgical infections and their
susceptibilities to antimicrobial agents. Special
references to bacteria isolated between April 1997
and March 1998. Japanese J Microbiol 2000;
53(80): 533-565.
14. Erol S, Altoparlak U, Akcay MN, Celebi F, Parlak M.
Changes of microbial flora and
wound colonization in burned patients. Burns 2004; 30(4): 357361.
15. Fadeyi A, Ismaila AA, Ganiyu AR. Bacteriological pattern
of wound swab isolates in patients with chronic
leg ulcer. Int J Health Res 2008; 1(4): 183-188.
16. Vimalin JH, Growther L. Studies on bacterial infections
of diabetic foot ulcers. Afr J
Clin Experimental
Microbiol 2010; 11(93): 146-149.
17. Lilani SP, Jangale N, Chowdhary A, Daver GB. Surgical
infection in clean and clean- contaminated cases.
Indian J Med Microbiol 2005; 23(4): 249-252.
18. Reichman DE, Greenberg JA. Reducing surgical site
infections: A review. Rev Obstetrics and Gynecol
2009; 2(4): 212-221.
19. Emine A, Hakan L, Mehmet D, Andreas V. Infection
control practice in countries with limited resources.
Ann Clin Microbiol Antimicrobials 2011; 10: 36-38.
20. Nwachukwu NC, Orji FA, Okike UM. Antibiotic
susceptibility patterns of bacterial
isolates from
surgical wounds in Abia State University Teaching
Hospital
(ABSUTH), Aba – Nigeria. Res J Med
Med Sci 2009; 4(2): 575-579.
21. Kehinde AO, Ademola SA, Okesola AO, Oluwatosin OM,
Bakare RA. Pattern of
bacterial pathogens in
burn wound infections in Ibadan, Nigeria. Ann
Burns and Fire Disasters 2004; 11(2): 34-39.
Trop J Pharm Res, August 2013;12 (4): 621